1. Field of the Invention
The present invention relates to the materials shaping and forming art, and, more particularly, to an improved cutting insert for fixed or rotary cutting tool operations.
2. Description of the Prior Art
Cutting inserts are utilized in a variety of material forming applications such as milling machines, lathes, shavers, and the like. In such applications the cutting insert is mounted on a tool body and the cutting edge of the cutting insert moves relative to the workpiece to remove a predetermined amount of material therefrom. The cutting insert may rotate relative to the workpiece, or may be non-rotating relative to the workpiece. Cutting inserts heretofore utilized have generally been cylindrical discs, in which a peripheral edge of the disc is utilized as the cutting edge. However, triangular, rectangular, or other geometric configurations of cutting tools have also been utilized.
The forces imposed upon the cutting insert during the cutting operation depend, of course, upon the relative speed of the cutting, the geometry of the cutting edge of the cutting insert with respect to the workpiece from which the material is being removed, and the material from which the workpiece is fabricated. Such factors as positive rake, negative rake, in both the radial and axial directions with respect to the cutter, the lead angle, and the like, all influence the total cutting force. In the general case, where there is a relative rotation between the workpiece and the cutting tool, as well as the relative longitudinal movement therebetween, the total force imposed upon the cutting insert is equivalent to the square root of twice the sum of the tangential force, radial force, and axial force imposed on the cutting tool. This force is applied to the cutting insert, and, in turn, is transmitted to the cutting insert holder in the tool utilizing the cutting insert. Depending upon the material being cut and other factors, as mentioned above, the force thus imposed upon the cutting insert can become quite large. When the cutting force exceeds the minimal sectional strength of the cutting insert, failure of the tool results. Consequently, depending upon the geometry, in many applications comparatively low cutting speeds and thin cuts may be all that the particular cutting insert can withstand. It is, of course, generally desirable to be able to have the capability of making as large a cut as rapidly as possible in order to minimize the total time of operation.
Cutting tools such as those shown in U.S. Pat. Nos. 1,542,007; 1,577,952; and 1,838,520 have generally not been able to withstand comparatively high cutting forces because of the particular geometry of the cutting edge of the cutting insert with respect to the workpiece and the load absorbing capability of the mounting structure of the cutting insert. The cutting tool shown in U.S. Pat. No. 4,213,358, which illustrates a rotating cutting tool, has the disadvantage of having a comparatively unsupported, narrow section adjacent the cutting edge, which limits the total force which may be applied to the cutting insert shown therein. This tends to limit the application of such a cutting insert.
Accordingly, there has long been a need for an improved cutting insert which is capable of withstanding comparatively high cutting forces without deterioration or degradation of the cutting insert or the mounting thereof, and to withstand such high cutting forces over comparatively long periods of time in order to provide a greater cutting insert life.